Classifications

• • H—ELECTRICITY
  • H01—ELECTRIC ELEMENTS
  • H01B—CABLES; CONDUCTORS; INSULATORS; SELECTION OF MATERIALS FOR THEIR CONDUCTIVE, INSULATING OR DIELECTRIC PROPERTIES
  • H01B3/00—Insulators or insulating bodies characterised by the insulating materials; Selection of materials for their insulating or dielectric properties
  • H01B3/18—Insulators or insulating bodies characterised by the insulating materials; Selection of materials for their insulating or dielectric properties mainly consisting of organic substances
  • H01B3/30—Insulators or insulating bodies characterised by the insulating materials; Selection of materials for their insulating or dielectric properties mainly consisting of organic substances plastics; resins; waxes
  • H01B3/46—Insulators or insulating bodies characterised by the insulating materials; Selection of materials for their insulating or dielectric properties mainly consisting of organic substances plastics; resins; waxes silicones
• • C—CHEMISTRY; METALLURGY
  • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
  • C08L—COMPOSITIONS OF MACROMOLECULAR COMPOUNDS
  • C08L83/00—Compositions of macromolecular compounds obtained by reactions forming in the main chain of the macromolecule a linkage containing silicon with or without sulfur, nitrogen, oxygen or carbon only; Compositions of derivatives of such polymers
  • C08L83/04—Polysiloxanes
• • C—CHEMISTRY; METALLURGY
  • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
  • C08G—MACROMOLECULAR COMPOUNDS OBTAINED OTHERWISE THAN BY REACTIONS ONLY INVOLVING UNSATURATED CARBON-TO-CARBON BONDS
  • C08G77/00—Macromolecular compounds obtained by reactions forming a linkage containing silicon with or without sulfur, nitrogen, oxygen or carbon in the main chain of the macromolecule
  • C08G77/04—Polysiloxanes
  • C08G77/12—Polysiloxanes containing silicon bound to hydrogen
• • C—CHEMISTRY; METALLURGY
  • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
  • C08G—MACROMOLECULAR COMPOUNDS OBTAINED OTHERWISE THAN BY REACTIONS ONLY INVOLVING UNSATURATED CARBON-TO-CARBON BONDS
  • C08G77/00—Macromolecular compounds obtained by reactions forming a linkage containing silicon with or without sulfur, nitrogen, oxygen or carbon in the main chain of the macromolecule
  • C08G77/04—Polysiloxanes
  • C08G77/20—Polysiloxanes containing silicon bound to unsaturated aliphatic groups
• • C—CHEMISTRY; METALLURGY
  • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
  • C08G—MACROMOLECULAR COMPOUNDS OBTAINED OTHERWISE THAN BY REACTIONS ONLY INVOLVING UNSATURATED CARBON-TO-CARBON BONDS
  • C08G77/00—Macromolecular compounds obtained by reactions forming a linkage containing silicon with or without sulfur, nitrogen, oxygen or carbon in the main chain of the macromolecule
  • C08G77/04—Polysiloxanes
  • C08G77/22—Polysiloxanes containing silicon bound to organic groups containing atoms other than carbon, hydrogen and oxygen
  • C08G77/24—Polysiloxanes containing silicon bound to organic groups containing atoms other than carbon, hydrogen and oxygen halogen-containing groups
• • C—CHEMISTRY; METALLURGY
  • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
  • C08G—MACROMOLECULAR COMPOUNDS OBTAINED OTHERWISE THAN BY REACTIONS ONLY INVOLVING UNSATURATED CARBON-TO-CARBON BONDS
  • C08G77/00—Macromolecular compounds obtained by reactions forming a linkage containing silicon with or without sulfur, nitrogen, oxygen or carbon in the main chain of the macromolecule
  • C08G77/70—Siloxanes defined by use of the MDTQ nomenclature
• • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
  • Y10—TECHNICAL SUBJECTS COVERED BY FORMER USPC
  • Y10T—TECHNICAL SUBJECTS COVERED BY FORMER US CLASSIFICATION
  • Y10T428/00—Stock material or miscellaneous articles
  • Y10T428/31504—Composite [nonstructural laminate]
  • Y10T428/31551—Of polyamidoester [polyurethane, polyisocyanate, polycarbamate, etc.]
  • Y10T428/31609—Particulate metal or metal compound-containing
  • Y10T428/31612—As silicone, silane or siloxane
• • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
  • Y10—TECHNICAL SUBJECTS COVERED BY FORMER USPC
  • Y10T—TECHNICAL SUBJECTS COVERED BY FORMER US CLASSIFICATION
  • Y10T428/00—Stock material or miscellaneous articles
  • Y10T428/31504—Composite [nonstructural laminate]
  • Y10T428/31652—Of asbestos
• • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
  • Y10—TECHNICAL SUBJECTS COVERED BY FORMER USPC
  • Y10T—TECHNICAL SUBJECTS COVERED BY FORMER US CLASSIFICATION
  • Y10T442/00—Fabric [woven, knitted, or nonwoven textile or cloth, etc.]
  • Y10T442/20—Coated or impregnated woven, knit, or nonwoven fabric which is not [a] associated with another preformed layer or fiber layer or, [b] with respect to woven and knit, characterized, respectively, by a particular or differential weave or knit, wherein the coating or impregnation is neither a foamed material nor a free metal or alloy layer
  • Y10T442/2475—Coating or impregnation is electrical insulation-providing, -improving, or -increasing, or conductivity-reducing
• • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
  • Y10—TECHNICAL SUBJECTS COVERED BY FORMER USPC
  • Y10T—TECHNICAL SUBJECTS COVERED BY FORMER US CLASSIFICATION
  • Y10T442/00—Fabric [woven, knitted, or nonwoven textile or cloth, etc.]
  • Y10T442/20—Coated or impregnated woven, knit, or nonwoven fabric which is not [a] associated with another preformed layer or fiber layer or, [b] with respect to woven and knit, characterized, respectively, by a particular or differential weave or knit, wherein the coating or impregnation is neither a foamed material nor a free metal or alloy layer
  • Y10T442/2926—Coated or impregnated inorganic fiber fabric
• • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
  • Y10—TECHNICAL SUBJECTS COVERED BY FORMER USPC
  • Y10T—TECHNICAL SUBJECTS COVERED BY FORMER US CLASSIFICATION
  • Y10T442/00—Fabric [woven, knitted, or nonwoven textile or cloth, etc.]
  • Y10T442/20—Coated or impregnated woven, knit, or nonwoven fabric which is not [a] associated with another preformed layer or fiber layer or, [b] with respect to woven and knit, characterized, respectively, by a particular or differential weave or knit, wherein the coating or impregnation is neither a foamed material nor a free metal or alloy layer
  • Y10T442/2926—Coated or impregnated inorganic fiber fabric
  • Y10T442/2992—Coated or impregnated glass fiber fabric

Definitions

• This invention relates to a method for manufacturing a rubber sheet having electrically insulating properties and thermally radiating properties.
• Heat-producing electronic components such as power transistors or thyristors usually generate heat in their operation.
• Heat-producing electronic components such as power transistors or thyristors usually generate heat in their operation.
• their properties deteriorate due to the heat and they occasionally fail.
• an electric-insulating and radiating sheet which exhibits both electric insulation properties and thermal conductivity is placed between the above-mentioned heat-producing electronic parts and constructed with radiator fins (or metal radiator plates) in order to provide the heat-producing electronic part in such a way that the heat generated will be radiated.
• Conventional radiating sheets are usually mica or a polyester film coated with grease.
• the grease can evaporate and is degraded in long-term use with the result that its radiating characteristics tend to degrade and it causes complications in operation.
• mica and polyimide films are hard and their surfaces are not adhesive.
• a conventional method for the production of an insulating and radiating rubber sheet reinforced with such a network insulating material is to dip the network material into a nonfluid (solid) peroxide-vulcanized silicone rubber compound dissolved in a large amount of solvent and the compound cured to a radiating rubber.
• the nonfluid rubber compound is not very soluble and a long time is required for dissolution and the solid component concentration in the resulting solution is low. Due to this, the number of immersions must be increased and the process becomes very complicated. Furthermore, this process poses safety and hygiene problems due to the use of a large amount of an organic solvent.
• a fluid addition reaction-curable silicone rubber composition is directly coated on a network insulating material and subsequently cured in order to effectively produce an electrically insulating and a thermally radiating rubber sheet which exhibits high strength.
• This invention relates to a method for manufacturing a rubber sheet which is electrically insulating and thermally radiating, comprising coating a network insulating material with a fluid silicone rubber composition and then curing said composition, where the fluid silicone rubber composition consists essentially of (a) 100 parts by weight of a polyorganosiloxane having a viscosity at 25° C. of from 0.1 to 100 Pa ⁇ s and having an average unit formula
• each R represents a monovalent hydrocarbon radical free of aliphatic unsaturation or a halogenated monovalent hydrocarbon radical free of aliphatic unsaturation
• each R' represents a monovalent aliphatically unsaturated hydrocarbon radical
• a has a value from 1.90 to 2.05
• b has a value from 0.0005 to 0.1
• the sum of a+b has a value from 1.91 to 2.06
• a polyorganohydrogensiloxane having a viscosity at 25° C. of 0.0007 to 5 Pa ⁇ s and having an average unit formula
• R is defined above, the sum of c+d has a value of 1.001 to 3, there is at least two silicon-bonded hydrogen atoms per molecule, and said polyorganohydrogensiloxane is present in an amount such that there are 0.5 to 10 equivalents of silicon-bonded hydrogen atoms per equivalent of aliphatically unsaturated hydrocarbon radical in (a), (c) from 100 to 500 parts by weight of alumina powder, and (d) a catalytic quantity of a platinum-group compound as a catalyst.
• Component (a) is crosslinked with component (b) in the presence of component (d) as a catalyst to form an elastomer.
• the silicon-bonded R in the average unit formula are monovalent hydrocarbon radicals such as alkyl radicals, such as methyl, ethyl, propyl, butyl, octyl, and cyclohexyl; aryl radicals such as phenyl and tolyl and halogenated monovalent hydrocarbon radicals such as halogenated alkyl radicals such as 3-chloropropyl and 3,3,3-trifluoropropyl.
• R' are monovalent aliphatically unsaturated hydrocarbon radicals such as vinyl, allyl, and 3-butenyl.
• the silicon atoms of this component may be bonded to extremely small amounts of other substituents such as hydroxyl and alkoxy in addition to R and R'.
• Example of siloxane units comprising this component are RR'SiO 2/2 , R 2 SiO 2/2 , RSiO 3/2 , R'SiO 3/2 , R 2 R'SiO 1/2 , RR 2 'SiO 1/2 , and SiO 4/2 .
• the molecular configuration of this component is usually straight chain; however, it may be partially branched.
• the aliphatically unsaturated hydrocarbon radicals of R' may be present at the molecular chain ends or as side chains or at both locations.
• R and R' are preferably present at the terminals from the standpoints of improved postcure mechanical properties.
• R and R' may each consist of a single type or may each consist of a mixture of two or more types.
• the polyorganosiloxanes of this composition may comprise a single type or a mixture of two or more types.
• Both the crosslinking density which can be varied by appropriately varying the mixing ratio of relatively low viscous polyorganosiloxane and relatively high viscous polyorganosiloxane and the quantity of inorganic filler are appropriately selected to satisfy the hardness specified for the cured silicone rubber. The desired product hardness can thus be advantageously obtained.
• the viscosity of the polyorganosiloxane regardless of whether it is a single type or a mixture of two or more types, is usually 0.1 to 100 Pa ⁇ s and preferable 0.2 to 50 Pa ⁇ s on average at 25° C.
• Component (b) plays the role of crosslinking agent for component (a).
• R groups directly bonded to silicon in this component are the same as for the R groups of component (a) and the R groups may be identical to the R groups of component (a).
• Examples of the siloxane units constituting this component are RHSiO 2/2 , R 2 SiO 2/2 , RSiO 3/2 , HSiO 3/2 , R 3 SiO 1/2 , R 2 HSiO 1/2 , and SiO 4/2 .
• This polyorganohydrogensiloxane may take the form of a straight chain, branched chain, network, or ring; however, a straight chain or ring is preferred.
• the R groups in each molecule may be a single type or a mixture of two or more types.
• the polyorganohydrogensiloxane may be a single type or a mixture of two or more types.
• the silicon-bonded hydrogen atoms may be located at the molecular chain ends or along the chain or at both of these two locations. In order to cure component (a), the quantity of silicon-bonded hydrogen atoms must be 0.5 to 10 equivalents per 1 equivalent of the aliphatically unsaturated hydrocarbon radical of component (a).
• the viscosity of component (b) is 0.0007 to 5 Pa ⁇ s at 25° C.
• the alumina powder comprising component (c) is expressed by the chemical formula Al 2 O 3 and is indispensable for imparting a high thermal conductivity and moderate viscosity and thickness to the silicone rubber composition of this invention.
• a typical alumina which is useful in this invention is the well-known calcined alumina( ⁇ -alumina) which can be produced by grinding a pulverizing the ⁇ -alumina produced by the heat treatment of aluminum hydroxide at elevated temperatures.
• the alumina to be used in the composition of this invention is desirably in the form of an extremely fine powder such as a particle size of ⁇ 50 ⁇ .
• the quantity of addition is 100 to 500 parts by weight and preferable 200 to 350 parts by weight per 100 parts by weight of component (a).
• this quantity is less than 100 parts by weight, the resulting radiating sheet does not exhibit an adequate thermal conductivity.
• the abovementioned quantity exceed 500 parts by weight, the resulting silicone rubber composition does not exhibit a satisfactory fluidity and, moreover, the vulcanized silicone rubber sheet suffers from degraded mechanical properties.
• the platinum-group compound catalyst to be used by the method of this invention as component (d) is a catalyst for the addition reaction of the silicon-bonded aliphatically unsaturated hydrocarbon radicals in component (a) with the silicon-bonded hydrogen atoms of component (b).
• the platinum-group compound as defined in this text is the individual platinum group metal and its compounds.
• platinum compound catalysts are preferred.
• the quantity of addition of platinum-group compound catalyst is 1 to 800 ppm as platinum-group metal based on the combined quantities of components (a) to (c).
• the fluid silicone rubber to be used by the method of this invention can be produced by blending the above-mentioned four components (a), (b), (c), and (d) to homogeneity.
• the mixer to be employed is arbitrary as long as the powder can be poured into and mixed with the liquid; however, it is preferable that the mixture be agitated under high shear forces. Because a mixture of components (a), (b), and (d) immediately begins to cure as soon as these components are mixed with each other, these three components should be mixed with each other immediately before molding.
• An addition-reaction inhibitor such as an organonitrogen compound, acetylene compound, or tin compound may be added to the above-mentioned composition to suppress the above-mentioned curing reaction from the standpoint of ease of operation.
• an additional thermally conductive filler such as zinc oxide, and boron nitride and other materials such as fine quartz powder, reinforcing silica fillers, heat stabilizers, flame retardants, or pigments can be added.
• the network insulating material includes woven fabrics, knits, nonwoven fabrics, and laminated products of these materials and may be any type as long as the material exhibits electric insulation. However, it should exhibit a good thermal conductivity and also exhibit a heat resistance in balance with the heat resistance of the silicone rubber. Examples are glass fibers, asbestos, and silicon carbide fibers.
• the fluid silicone rubber composition is preferably coated on both surfaces of the network insulating material.
• the coating method is arbitrary; however, a preferred coating method is a doctor-blade method in which coating is carried out under an extremely low pressure.
• the fluid silicone rubber composition can be efficiently cured at elevated temperatures of 70° to 180° C. by either press vulcanization or hot-air vulcanization; however, in a preferred process a fluid silicone rubber composition which has been coated by a doctor blade is passed continuously through a heating oven.
• doctor-blade coating can be smoothly carried out. Moreover, dip coating can also be smoothly carried so that the electrical insulating and thermal radiating rubber sheet can be manufactured with only a few immersions and a subsequent curing process.
• the organic solvent to be used includes toluene, xylene, halogenated hydrocarbons such as 3,3,3-trichloroethane and tetrachloroethylene, acetone, and methyl ethyl ketone and the quantity should be 1 to 20 wt% of the silicone rubber composition.
• the silicone rubber composition When a small quantity of the above-mentioned organic solvent is added to the silicone rubber composition, the silicone rubber composition would be heated at a relatively low temperature in order to evaporate the organic solvent and then completely cured by heating at a higher temperature.
• an electric insulating and thermal radiating rubber sheet of higher strength can be efficiently manufactured.
• the electrically insulating and thermally radiating rubber sheet produced by the production method of this invention not only exhibits high strength because the silicone rubber has thoroughly penetrated into and become unified with the network insulating material, but also does not suffer from peeling of the silicone rubber from the network insulating material even with repeated flexural loading of the sheet. Also, its thermal radiative property does not decline even in the presence of the network insulating material. These characteristics can be further improved by the preliminary addition of a small amount of an organic solvent to the fluid silicone rubber composition.
• the electrically insulating and thermally radiating rubber sheet produced by the method of this invention may be optionally cut into pieces of the desired shape and then installed between the heat-producing electronic component and a radiator fin (or metal radiator plate) with the result that the heat generated by the electronic component can be efficiently radiated.
• Parts in the examples denotes “parts by weight” and the physical properties such as the viscosity were all measured at 25° C.
• the viscosity was measured using a BH rotary viscometer and the tensile strength, volume resistivity, and breakdown strength were measure by the methods of JIS K 6301.
• the dissolution time as defined in this text is the time required for the dissolution to homogeneity of the silicone rubber composition.
• the thermal resistivity was measured by attaching a TO-3 power transistor to a radiator via an insulating and radiating rubber sheet of this invention, and the units °C./w are degree centigrade per watt.
• the fluid silicone rubber composition (I) was coated, either directly or optionally diluted with toluene, on one side of a glass cloth (thickness, 0.2 mm) using a doctor blade and then was continuously moved through a heating oven at 130° C. for hot-air vulcanization with a residence time of 5 minutes. Composition (I) was then similarly coated on the other side of the glass cloth and subsequently hot-air vulcanized.
• the composition containing toluene was heated by warm air at 30° to 40° C. in order to evaporate the toluene and then hot-air vulcanized at 130° C.
• a conventional insulating and radiating rubber sheet was produced by pouring fluid silicone rubber composition (I) into a 0.31 mm deep mold, smoothing the surface with a doctor blade and subsequently hot-air vulcanizing at 130° C. for 5 minutes.
• a dimethylvinylsilyl-terminated polydimethylsiloxane 120 parts; vinyl group content, 0.30 wt%; viscosity, 2 Pa ⁇ s
• a fumed silica 20 parts; BET surface area, 200 m 2 /g
• hexamethyldisilazane 7 parts
• the resulting base compound was combined with ⁇ -alumina (250 parts; average particle size, 2.2 ⁇ ), a polymethylhydrogensiloxane (4.6 parts; viscosity, 0.007 Pa ⁇ s) with the general formula
• composition (II) was coated, directly or optionally diluted with xylene, on one surface of a glass cloth (thickness, 0.1 mm) using a doctor blade and then continuously moved through a heating oven for hot-air vulcanization at 150° C. with a residence time of 3 minutes.
• Composition (I) was then coated on the other surface of the glass cloth by the same method as above and subsequently hot-air vulcanized.
• the composition containing xylene was treated with warm air at 30° to 40° C. in order to evaporate the xylene and was then hot-air vulcanized at 150° C.
• a conventional insulating and radiating rubber sheet was manufactured by pouring fluid silicone rubber composition (II) into a 0.21 mm deep mold, smoothing the surface with a doctor blade and then hot-air vulcanizing at 150° C. for 3 minutes.
• the data on the production process and properties of the electrically insulating and thermally radiating rubber sheet products are reported in Table 2.
• An polyorganosiloxane gum (100 parts; degree of polymerization, 5000; dimethylsiloxane units, 99.84 mol %; methylvinylsiloxane units, 0.16 mol %) was combined with a hydroxyl terminated polydimethylsiloxane (7.0 parts; viscosity at 25° C., 0.00004 m 2 /s) and a fumed silica (20 parts; BET surface area, 200 m 2 /g) as a reinforcing filler. The resulting mixture was heated while being kneaded.
• nonfluid (solid) silicone rubber composition (III) could not be directly coated on a glass cloth (thickness, 0.1 mm) using a doctor blade, it was dissolved in and diluted with xylene. The resulting solution was coated on a glass cloth by the method of Example 1 and subsequently hot-air vulcanized to obtain an insulating and radiating rubber sheet.
• the data on the production process and the properties of the insulating and radiating rubber sheet product are shown in Table 3.
• an insulating and radiating rubber sheet with high strength can be simply and effectively manufactured by the method of this invention.
• a fluid silicone rubber composition (IV) and then an electrically insulating and thermally radiating rubber sheet were produced by the methods of Example 1 with the exception that a dimethylvinylsilyl-terminated polymethyl(3,3,3-trifluoro-propylsiloxane (viscosity, 10 Pa ⁇ s) was used instead of the dimethylsiloxane-methylvinylsiloxane-methylphenylsiloxane copolymer of Example 1 and methyl ethyl ketone was used instead of toluene.
• a dimethylvinylsilyl-terminated polymethyl(3,3,3-trifluoro-propylsiloxane viscosity, 10 Pa ⁇ s

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• Health & Medical Sciences (AREA)
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• Compositions Of Macromolecular Compounds (AREA)
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• Insulating Bodies (AREA)
• Processes Of Treating Macromolecular Substances (AREA)
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• 1982
  • 1982-06-14 JP JP57101895A patent/JPS58219034A/ja active Pending
• 1983
  • 1983-06-13 US US06/503,911 patent/US4486495A/en not_active Expired - Lifetime

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